• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.283-286
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• 2003

The electric traction load is quite differ from general power system load which is single-phase, high-speed heavy load receiving power from 3-phase power system and also has variable load characteristics over time and space. Therefore, there are inevitably power quality problems such as steady state or transient voltage drop, voltage imbalance and harmonic distortion. In addition, it is expected that transient voltage sag could affect the safety of feeding system. Thus, in this paper transient analysis and voltage sag compensation of AT(Auto Transformer) feeding system are studied. The fault study of traction network is analysed by using PSCAD/SMTDC simulation tool. In addition, application of DVR in electric traction system is proposed to compensate the voltage sag of traction network which is occurred by the fault of utility source. The results of fault study will be a useful research works for operation and setting of electric traction relay. Also, it can be shown that application of the DVR in electric system is very useful to compensate the voltage sag from the result of related simulated work. The results of study will be a useful research works for management and planning of power quality in electric traction system.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.65-67
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• 2002

The gas metal arc welding(GMAW) is regarded as one of the best candidate for welding automation in industrial joining application. It is important to monitor the weld quality for the high performance of weld automation. The measured analog signal is frequency analyzed by digital signal process method. In order to observe the welding phenomena and control welding condition, arc light, voltage, and current are measured at the same time. They are analyzed and compared with arc sound. for these experiments, a power source of constant voltage characteristics was used in the pure metal transfer mode.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.411-413
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• 2005

Static approaches usually employed in voltage stability analysis are based on the pre-determined scenarios of varying load and generation patterns. Thus, even though the approaches are applied to the same system condition, one may obtain different voltage instability phenomena using different scenarios. In the stage of concrete control strategy determination against voltage instability, dynamic approaches with full-time and/or quasi steady-state simulations need to be applied in order to confirm the effectiveness of the established control strategies. This paper describes the ULTC and dynamic load models, and discusses characteristics of the models.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.1697-1700
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• 2006

A Novel pixel structure with a new threshold voltage compensation technique is proposed for large-size a-Si:H AMOLED panel application. The proposed pixel improves image quality with threshold voltage compensation and alleviates annealing technique for display-off time. Sensing the threshold voltage of driving TFT for 20-inch WUXGA panel is verified by the HSPICE simulation.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.1
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• pp.48-52
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• 2011

Over the years, traditionally, six-switch three-phase inverters have been widely utilized for variable speed alternating current motor drives. Recently, some efforts have been made on the application of four-switch three phase inverter for uninterruptible power supply and variable speed drives. This is due to some advantages of the four-switch three phase inverter over the conventional six-switch three-phase inverters such as reduced price due to reduction in number of switches, reduced switching losses, reduced number of interface circuits to supply logic signals for the switches, simpler control algorithms to generate logic signals, less chances of destroying the switches due to lesser interaction among switches, and less real-time computational burden. However such as slow di/dt and speed limitation, are the inherent characteristics and main drawbacks of the four-switch configuration. Those problems can be overcome in conjugation with Voltage-doublers which has additional advantage, such as unity power factor correction.

• Journal of the Korean Society for Heat Treatment
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• v.21 no.4
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• pp.199-204
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• 2008

The destructive method is reliable and widely used for evaluating the properties of material but it is time-consuming and difficult to prepare specimens from in-service industrial facilities. In the present research, Barkhausen Noise (BN) has been used to evaluate changes of mechanical properties due to heat treatment condition. The BN voltage (rms voltage) was measured with grain size. The rms voltage of BN increased with the heat treatment temperature ($870{\sim}1000^{\circ}C$) because the grain size increased with the temperature. The rms voltage of BN decreased with various heat treatment processes, such as quenched, tempered and PWHT. The BN can be used for the nondestructive evaluation of the forged reactor vessels. and moreover, it may be effectively used in the field application.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.10
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• pp.695-702
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• 1987

Nowadays as the power systems have been more complicated and have grown to ultra high voltage, it requires a accurate and high speed relaying scheme to improve the reliability and stability of power systems for a harmonious power supplying. For this purpose voltage and current have to be measured at the location of the protective device and the short circuit impedance must be determined. This paper presents the application methods and some results of digital distance relaying scheme which is based upon the theouy of real-time symmetrical components. Usually the symmetrical component have been used to solve the transient systems as well as the steady state systems under unbalanced systems. But, real-time symmetrical component frequently have not been applied to on-line control region of the large power system. We have tried to apply this method to deal with the various type of faults on artificial transmission line. And experimental results demonstrate the validity of the proposed techniques. Therefore, this study is expected that it is contributed to improve the reliability of power supplying, searching for the fault location rapidly and exactly in power system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.563-566
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• 2004

We have studied a electrically controlled birefringence (ECB) mode for field sequential liquid crystal display (FSLCD). We measured response time of the ECB mode. The ECB mode exhibiting fast response time, high transmittance, low operating voltage and adequate viewing angle. The positive liquid crystal (LC) is better than negative LC on dielectric anisotropy, birefringence and rotational viscosity. So that, the ECB mode is one of strongest candidate for FSLCD application.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.89-90
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• 2006

In this paper, the authors propose the RTDS (Real Time Digital Simulator) simulation method which puts a real HTS (High Temperature Superconducting) tape into the simulated voltage feedback system of HTS tape. To perform the RTDS based simulation, the voltage feedback system of HTS tape with hardware is designed and connected to the RTDS. This simulation method is the world first in order to obtain much better for installation of HTS power cable into a utility network.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.9
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• pp.609-615
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• 1987

The optimal operation of power system is developed by alternately using real power dispatch and reactive power dispatch problem. The real power system scheduling process is formulated as an optimization problem with linear inequality constraints. A.C. loadflow method is used for the problem solution and line losses are considered. The constraints under consideration are generator power limits, load scehdling limits and line capacity limits. In solving the objective function the Dual Relaxation method is adopted. Tests indicate that the method is practical for real time application. The reactive power control problem uses the Dual Simplex Relaxation method as in the real scheduling case. Insted of minimizing the cost of power system, the objective is selected as to determine the highest possible voltage schedule. The constraints under consideration are the voltage limits at each node and the possibilities of supply or absobtion of reactive energy by generator units and the compensation facilities. Tests indicate that the method is practical for real time applications. The overall optimization methods developed in this paper proved to obtained fine results in minimizing object function compared with the method without using voltage control. And the overall voltage profiles were also improved.